IRVING — Tony Romo sat alone on the Dallas bench, his stare frozen at the ground on a cold night in Washington.

Any number of things could have been going through the mind of the Cowboys quarterback in the final minutes of a 28-18 loss to the Redskins on Sunday night — his third playoffs-or-bust failure in five years in a finale against an NFC East rival.

Maybe it was his latest big mistake in a huge moment, an interception that helped Washington clinch the win. Or his famous flub on the hold for what could have been a game-winning field goal in his first playoff game six years ago at Seattle. Or that the Cowboys still had a chance so late in a season notable for the death of a teammate and injuries to so many key players.

“It stings,” said Romo, who dropped to 1-6 in elimination games with Dallas. “You put your heart into this thing for so long, throughout the year, this offseason. We had to overcome a lot of stuff just to get ourselves in this situation.”

The words of tight end Jason Witten when he arrived at training camp — “can’t be the same old story” — haunt the Cowboys now because it was. Mistakes and poor game management cost them some wins early in the season. Interceptions — nine of them — piled up on Romo in two losses. After winning five of six to regain control of their playoff fate, the Cowboys dropped the last two.

In the recent series of winner-take-all finales, the Cowboys have been swept by their three division rivals. Philadelphia blew them out in 2008, and the New York Giants took a 21-0 lead in a 31-14 victory last season.

Romo had the ball 85 yards from the end zone against the Redskins, with plenty of time to lead a scoring drive that could have ended a two-year playoff drought. Instead, he floated a pass that leaping Redskins linebacker Rob Jackson grabbed, and now Dallas is missing the postseason for the fourth time in Romo’s six full seasons as the starter.

Dallas has become the definition of mediocrity, finishing 8-8 for the second year in a row and now holding a record of 128-128 since the start of the 1997 season. That means 2013 will be the third straight year with a record that starts at an even .500 going back more than a decade. Dallas has one playoff win in that span.

“If we don’t do a good enough job then it is the same old story,” Witten said Monday in a quiet and mostly empty Cowboys locker room. “We’ve just got to stomach it up and get better because of it. That’s the only way to get to the top.”

Much has changed since Dallas was 3-5 and facing early playoff elimination. In the midst of the 5-1 stretch that vaulted them to a tie for the division lead, the Cowboys had to play through the death of practice squad linebacker Jerry Brown in a car accident that led to intoxication manslaughter charges against nose tackle Josh Brent.

The wreck happened hours before Brent was supposed to be on the team plane to Cincinnati, where he was expected to start in place of injured Jay Ratliff. Dallas scored 10 points in the fourth quarter and beat the Bengals 20-19 on a field goal by Dan Bailey as time expired.

That turned out to be the first of three straight games decided on the final play, with the Cowboys splitting back-to-back overtime games at home by beating Pittsburgh and losing to New Orleans.

Questions about coach Jason Garrett’s job disappeared as he steered the team through the death of Brown and the wins kept coming. Cowboys owner Jerry Jones lauded Garrett’s leadership, and while Jones hasn’t directly said Garrett will return, he has said he was never really considering an alternative.

Now the question is whether these Cowboys will be remembered for perseverance or failure.

“I think we’ll probably remember it for both of those things,” Garrett said. “These players and coaches went through a lot this year, overcame a lot of adversity, handled things the right way, got stronger as a result of it and that’s really a special thing to be a part of.”

Injuries picked part the Dallas defense most of the season, but it was the offense’s turn against the Redskins. Receivers Dez Bryant, Miles Austin and Dwayne Harris were sidelined at various times, and Bryant spent the night in a hospital after injuring his back late in the game.

Bryant, who had a breakout season with 1,382 yards and 12 touchdowns, was moving gingerly on crutches at team headquarters Monday. Austin and Harris had sprained ankles.

The defense, which gave up 200 yards rushing to Washington rookie Alfred Morris, will eagerly await the return of inside linebackers Sean Lee and Bruce Carter, along with three other starters who missed significant time.

“Eventually, we’re going to get this thing right,” said cornerback Brandon Carr, who signed a $50 million free agent contract this year. “This offseason is going to be turned up a few more notches than last offseason. I don’t accept losing and none of the guys in this locker room accepts losing and we’re tired of this feeling.”